BCC 鉄中の自己格子間原子のソリトン的運動と衝突に関する研究

Abstract

Self-interstitial atoms (SIAs) in bcc iron display unusual migration behaviors; strong anisotropy toward a direction with occasional rotation to an equivalent direction as well as retracing the same way as it has come, and also ultra-high mobility when they are clustered. These singularities cannot be explained by simple interstitial or interstitialcy diffusion mechanisms. However, some of them will be well accounted if the SIA could behave as a soliton, which makes three-dimensional movements in appearance, but essentially a serial combination of one-dimensional migration. Indeed, a crowdion, one of the isomeric configurations of the SIA, has an atomic arrangement very similar to the one-dimensional dislocation core structure, whose migration kinetics has been well modelled by a one-dimensional soliton equation. Here we report a decisive observation that both a single and colliding two crowdions really behave as solitons in iron crystals using molecular dynamics simulations. In addition, we ascertain that the present results are attributed to the intrinsic nature of the crowdion where an overall potential felt by atoms therein is very shallow and periodical along the migration direction.